The present disclosure relates to a video-based method and system for determining a length of an available parking space at a given instant in time. The disclosure finds application in parking space management. However, the embodiments are also amendable to other like applications.
One challenge associated with on-street parking is an accurate detection of available spaces made by drivers and/or parking managers. Conventional methods for detecting vehicle occupancy in parking spaces include sensor-based solutions, such as “puck-style” sensors and ultrasonic ceiling or in-ground sensors. These sensors are costly to install and maintain. Because the sensors are located directly in the parking region, parking availability may be reduced during service work.
Non-stereoscopic video cameras have also been proposed to monitor on-street parking. Like the in-ground sensor technology, the early proposal of video camera technology was designed for, and limited to, monitoring a single-space parking configuration known as stall-based parking, where painted lines typically demark a defined parking space for a single vehicle. However, on-street parking can be provided in a multi-space configuration, where a long section of street is designated as a parking area to accommodate multiple vehicles parked along any portion of the parking area. An extension of the video camera technology for use in multi-space, on-street parking occupancy detection is recently being developed, and the present disclosure is a part of this technology development.
Multi-space parking configurations are advantageous over single space configurations because they require easier maintenance and lower costs. The application of sensor-based methods in multi-space parking environments is conceptually difficult and expensive to implement. Given a comparatively lower cost of a video surveillance, a video-based solution offers better value when incorporated into a parking management scheme. One video camera located near the parking region can monitor and track several parking spots. Additionally, maintenance of the video cameras is likely to be less disruptive to street traffic than maintenance of in-ground sensors.
Co-pending and commonly assigned application U.S. Publication No. 2013/0265419, entitled “A System And Method For Available Parking Space Estimation For MultiSpace On-Street Parking”, filed Apr. 6, 2012, introduced a video-based method operable to analyze frames in a video feed for estimating whether a parking space that appears available can actually fit a vehicle. Because a camera can have a viewing angle with respect to the parking street that varies from one street to another, U.S. Ser. No. 13/441,269 applied a side detection operation for detecting a vehicle from a side of the vehicle. Because objects with similar physical sizes can appear as different sizes on the image plane, depending on their positions relative to the image capture device, the computed length of an object can vary depending on its location in the parking region. FIG. 1 shows an example scenario where two sedans of similar size are parked in a parking lane. It clearly shows the variation of vehicle size as a function of the vehicle's distance from the image capture device. FIG. 2 shows the example detection in the PRIOR ART where the vehicles appear as different sized objects on the image plane. The objects located farther from the image capture device become smaller in appearance, and therefore are susceptible to noise. These vehicles may be mistaken as non-vehicle objects and/or occlusions in the known vehicle detection process.
The previously introduced video-based operation does not account for effects of object location on the image plane. An improved method is needed which resizes spatial information to aid vehicle and parking space detection in an on-street parking environment.